As an important industrial chemical and solvent, anhydrous ethanol plays an immeasurable role in national economy. With the rapid growth of market demand and continuous improvement of product quality needs, the methods of anhydrous ethanol production are constantly improving and developing. Preparation methods of anhydrous ethanol are traditional calcium oxide and ion exchange technique at the earliest, benzene azeotropic distillation technique, pentane azeotropic technique, extractive distillation technique, molecular sieve technique etc. Though azeotropic distillation technique and extractive distillation technique can produce high-concentrated ethanol, these methods inevitably have the trace of Organic dissolved impurities, moreover with big investment, high consumption, low rate relatively.
Adsorption method by using adsorbent has been industrialized since the 1980s with a new alcohol dehydration technology. Adsorbents are activated carbon, silica gel, activated alumina, molecular sieve, cereal powder and so on. Among them molecular sieve adsorption have the best capacity and selectivity. Meanwhile it has good thermal stability and fine mechanical performance, with no swelling after adsorption and no ravel because of wet. The adsorbent has a long life, up to 5-7 years. Therefore this technology has been widely applied.
ZL 88102169, CN 1498678 (application number is 02150135.1), CN 1328987A (application number is 01118051.X), U.S. Pat. No. 4,465,875, U.S. Pat. No. 4,407,662 and other patents relate to anhydrous ethanol production by adsorption. However, the feed method nowadays is feeding from below, which cause the gas stir up and the layer of adsorption bed displace. The product often carries over adsorbent, which influence the life of adsorbent. Meanwhile In the production of anhydrous ethanol, cooling water costs a lot because of steam generation and cooling process. In addition, when desorbed gas cool down instantaneously, the usage of cooling water and heat exchange surface area are great because of focused desorption, which cause large equipment loading, great energy, great investment in equipment and high operating costs. In the course of desorption, the valve is opened and closed directly, which makes gas generate momentum. And it can easily cause adsorbent pulverization. The instantaneous heat is great, and the heat exchange surface area is large in unit time.